Numerical determination of the forming limit curves of anisotropic sheet metals using GTN damage model

Kami, Abdolvahed; Dariani, Bijan Mollaei; Vanini, Ali Sadough; Comşa, Dan Sorin; Banabic, Dorel

doi:10.1016/j.jmatprotec.2014.10.017

Cited by 115 publications

(62 citation statements)

References 36 publications

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“…It is worth noting that, in the case of the Erichsen deep drawing test, the initiation of necking does not necessarily occur in the central area for all specimens. This feature, which depends on the specimen width and the contact between the punch and the specimen, is consistent with the experimental observations (see, e.g., [41]). …”

Section: Numerical Criteria For the Prediction Of The Occurrence Of Nsupporting

confidence: 92%

Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes

Chalal

Abed‐Meraim

2017

Metals

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Abstract:In this work, three numerical necking criteria based on finite element (FE) simulations are proposed for the prediction of forming limit diagrams (FLDs) for sheet metals. An elastic-plastic constitutive model coupled with the Lemaitre continuum damage theory has been implemented into the ABAQUS/Explicit software to simulate simple sheet stretching tests as well as Erichsen deep drawing tests with various sheet specimen geometries. Three numerical criteria have been investigated in order to establish an appropriate necking criterion for the prediction of formability limits. The first numerical criterion is based on the analysis of the thickness strain evolution in the central part of the specimens. The second numerical criterion is based on the analysis of the second time derivative of the thickness strain. As to the third numerical criterion, it relies on a damage threshold associated with the occurrence of necking. The FLDs thus predicted by numerical simulation of simple sheet stretching with various specimen geometries and Erichsen deep drawing tests are compared with the experimental results.

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Section: Numerical Criteria For the Prediction Of The Occurrence Of Nsupporting

confidence: 92%

Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes

Chalal

Abed‐Meraim

2017

Metals

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“…The results showed that there was a good correlation between the FE prediction and experiments, especially in the biaxial strain state (high stress triaxiality) [20,22] due to the high stress triaxiality ratio created by this state. It also clear that the ability of the Nakajima test to describe the fracture in ISF is still debatable; some researchers claim that the test is identical to that constructed from ISF tests on pyramidal and conical truncate parts [8], while others proved that the major strain at fracture in ISF is located above the Nakajima's FLCF when a small tool dimeter is used [9].…”

Section: Introductionmentioning

confidence: 83%

“…The fracture in the Nakajima test was predicted using the original GTN model, which showed good agreement with the experimental Nakajima test for all strain states. The original anisotropic GTN model was implemented in ABAQUS/Explicit by Kami et al [22] to construct the FLD of an anisotropic aluminium sheet using the Nakajima test. The result of the original anisotropic GTN model showed a better correlation with the experimental Nakajima test, especially in the biaxial tension strain state.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of formability and fracture of pure titanium in incremental sheet forming

Gatea

et al. 2017

Int J Adv Manuf Technol

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A forming limit diagram (FLD) is commonly used as a useful means for characterising the formability of sheet metal forming processes. In this study, the Nakajima test was used to construct the forming limit curve at necking (FLCN) and fracture (FLCF). The results of the FLCF are compared with incremental sheet forming (ISF) to evaluate the ability of the Nakajima test to describe the fracture in ISF. Tests were carried out to construct the forming limit diagram at necking and fracture to cover the strain states from uniaxial tension to equi-biaxial tension with different stress triaxialities-from 0.33 for uniaxial tension to 0.67 for equi-biaxial tension. Due to the fact that the Gurson-Tvergaard-Needleman (GTN) model can be used to capture fracture occurrence at high stress triaxiality, and the shear modified GTN model (Nahshon-Hutchinson's shear mechanism) was developed to predict the fracture at zero stress or even negative stress triaxiality, the original GTN model and shear modified GTN model may be not suitable to predict the fracture in all samples of the Nakajima test as some samples are deformed under moderate stress triaxiality. In this study, the fractures are compared using the original GTN model, shear modified GTN model and the Nielsen-Tvergaard model with regard to stress triaxiality. To validate the ability of these models, and to assess which model is more accurate in predicting the fracture with different stress triaxialities, finite element (FE) simulations of the Nakajima test were compared with an experimental results to evaluate the applicability of the Nakajima test to characterise the fracture from ISF. The experimental and FE results showed that the shear modified GTN model could predict the fracture accurately with samples under uniaxial tension condition due to low stress triaxiality and that the original GTN model is suitable for an equi-biaxial strain state (high stress triaxiality), whereas the stress triaxiality modified GTN model should be considered for samples which have moderate stress triaxiality (from plain strain to biaxial strain). The numerical and experimental FLCF of pure titanium from the Nakajima test showed a good agreement between the experimental and numerical results of ISF.

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“…This strategy allows delimiting the limit strains for stretched sheet metals that should not be exceeded in order to ensure a good quality of the final product. The FLDs are determined using necking or fracture criteria, which may be based on sound theoretical developments (see, e.g., Hill, 1952;Stören and Rice, 1975;Yamamoto, 1978;Abed-Meraim et al, 2014) or on finite element (FE) simulations (see, e.g., Zhang et al, 2011;Lumelskyy et al, 2012, Martínez-Donaire et al, 2014Kami et al, 2015). These criteria are generally combined with constitutive models for the prediction of limit strains in sheet metal forming.…”

Section: Determination Of Forming Limit Diagrams Based On Ductile Dammentioning

confidence: 99%

Determination of Forming Limit Diagrams Based on Ductile Damage Models and Necking Criteria

Chalal

Abed‐Meraim

2017

Lat. Am. j. solids struct.

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Numerical determination of the forming limit curves of anisotropic sheet metals using GTN damage model

Cited by 115 publications

References 36 publications

Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes

Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes

Evaluation of formability and fracture of pure titanium in incremental sheet forming

Determination of Forming Limit Diagrams Based on Ductile Damage Models and Necking Criteria

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